The invention relates to devices for well drilling, and more particularly, to devices for processing plugging and grouting materials and for their application to the walls within a pre-set interval of the well.
One of important reasons hampering the improvement of drilling efficiency resides in the occurrence of troublesome zones in wells associated with instability in the rocks forming the well walls or with absorption of flushing fluid. In addition to high consumption of expensive plugging materials, liquidation of troublesome zones results in considerable unproductive loss of working time and in idling of drilling equipment. Therefore much emphasis is now placed on the development of new methods and equipment for the liquidation of troublesome zones and lowering of losses caused by such troubles.
A method for the liquidation of troublesome zones using highly-concentrated dry quick-setting materials processed directly within the troublesome interval of the well improves to a large degree the efficiency of drilling, but such method is also associated with additional labour consumption mainly in connection with lowering and lifting operations. This labour effort is especially great in liquidating troublesome zones when drilling wells with the employment of removable core lifters, wherein the number of lowering and lifting operations for the drilling process proper is minimized.
Known in the art is a device for applying plugging mix to well walls which is lowered in the well on drill pipes. The device comprises an adapter designed for coupling to a drilling string, the adapter being rigidly coupled on the other side to a mud saver bucket which is made in the form of an auger carrying a bit for drilling-off plugging mix at its distal end (cf. USSR Inventor's Certificate No. 451835, Int.Cl. E 21B 33/13).
When this device is used, the main drilling bit employed for drilling the well is first withdrawn from the well, and replaced by the above-described device. Before lowering the device, a plugging material is fed into the well. All these operations result in considerable unproductive time losses, hence in lower productivity.
Known in the art is a device for applying plugging mix, comprising a pipe for accommodating the mix, which is rigidly coupled by means of an adapter to a drilling string, the pipe being sealed with a plug at the bottom during its transfer. A head and a piston are installed in series in the pipe over the plugging mix, the head and the piston being rigidly connected to one another. The head has passages for the flow of a fluid, a bit for drilling-off plugging mix, and vanes for applying the mix to the well walls. The piston has passages for the flow of the fluid and accommodates spring-biased locking members for fixing the position of the head with respect to the drilling string. The vanes of the head in this device are made in the form of a helical spiral with turns of the hand opposite to the direction of rotation of the drilling string (cf. USSR Inventor's Certificate No. 685808, Int.Cl. E 21 B 33/13). In operation of this device the plugging material is fed to a troublesome zone concurrently with the device for its processing and application to the well walls.
However, the employment of this device also results in additional time losses associated with the head to withdraw the main drilling implement from the well and to replace it with devices for applying plugging mix together with plugging mix.
As mentioned above, such time losses are especially important in drilling wells with the employment of a removable core lifter when the whole drilling string is only withdrawn from the well in case it is required to replace the worn drilling bit.
It is an object of the invention to improve the efficiency of drilling, that is to reduce time losses for unproductive operations.